This invention applies to a category of self-propelled, climbing vehicles that primarily make use of wheels or endless tracks to provide propulsion along a climbing surface, but could employ legs. For this purpose, the term climbing vehicle refers to a vehicle that is capable of traversing a surface horizontally or vertically in some inclined or inverted position relative to the earth horizon. Further, it is intended that the climbing vehicle is able to accommodate irregularity in the climbing surface including convex or concave regions. Such climbing vehicles may be used to conduct remote operations such as inspection, maintenance, or manufacturing in environments that pose difficulty or danger for human operation. These climbing vehicles could also be used in a wide variety of applications including power production, civil structures, or shipbuilding. A variety of climbing vehicles have been proposed to operate in these conditions. The methods of achieving mobility for climbing vehicles include but are not limited to legged locomotion, endless tracks or wheeled devices. Patent literature demonstrating examples of climbing vehicles employing endless tracks include U.S. Pat. No. 3,960,229, U.S. Pat. No. 4,789,037, U.S. Pat. No. 4,828,059, U.S. Pat. No. 5,366,038, U.S. Pat. No. 5,435,405, U.S. Pat. No. 5,487,440, U.S. Pat. No. 5,884,642, U.S. Pat. No. 5,894,901, U.S. Pat. No. 6,889,783, U.S. Pat. No. 7,498,542 B2, U.S. Pat. No. 7,775,312, and US application publication numbers US 2012/0111649 A1, US 2012/0116583 A1, US 2012/0111843 A1. Patent literature demonstrating examples of climbing vehicles employing wheels include U.S. Pat. No. 3,690,393, U.S. Pat. No. 3,810,515, U.S. Pat. No. 4,010,636, U.S. Pat. No. 5,049,218, U.S. Pat. No. 5,355,807, U.S. Pat. No. 5,853,655, U.S. Pat. No. 6,000,484, U.S. Pat. No. 6,564,815, US 6,59622, U.S. Pat. No. 6,595,152, U.S. Pat. No. 6,627,004 B1 2003, U.S. Pat. No. 6,688,938, U.S. Pat. No. 6,793,026, U.S. Pat. No. 6,886,651, and US application publication numbers US 2009/0078484, U.S. Pat. No. 7,309,464 B2, US 2010/0212983 and US 2010/017610. The majority of the wheeled-type climbing vehicles employ magnets in the wheel portion as demonstrated in U.S. Pat. No. 2,694,164. Advanced features in magnetic wheels have been demonstrated, for example as in U.S. Pat. No. 6,125,955. The use of wheels in climbing platforms provides several advantages, including relative simplicity in their design and actuation, and constant pitch properties that contribute to uniform motion transfer. The primary difficulty in using a wheeled-type platform for climbing is that the wheels require theoretical point contact with the surface to enable efficient rolling. This point contact limits the region in which adhering elements can connect or be in close proximity to the climbing surface. Adhering elements may be made of magnets, suction cups, adhesive or other device that can create an adhering force to the climbing surface. The size of the contact region for adhering members is generally related to the amount of adhering force that can be generated.
The size of the available contact region for wheeled climbing vehicles can be increased by increasing the number of wheels in contact with the climbing surface to yield an increase in the overall adhering force of the vehicle. For example, when magnets are used as adhering members, they may be embedded in the wheel to rotate with the wheel (U.S. Pat. No. 2,694,164), or they may be suspended to the wheel axis but have the ability to move circumferentially about the wheel (US pat. App. 0212983). While the overall adhering force of the vehicle can be increased by increasing the number of wheels in contact with the climbing surface, this raises several technical difficulties in the design and implementation of these systems. First, as the number of wheels increases, the complexity of the system increases. Second, as the number of wheels in contact with the climbing surface increases beyond a minimal number, for example three to provide stability when the contact surface is non-planar, wheel suspensions are required to ensure wheel contact with the surface. Third, as the number of wheels in contact with the surface increases, the kinematic requirements for steering increase, or slipping is introduced into the system which decreases efficiency. For these reasons, climbing vehicles with large numbers of wheels that have the adhering members integrated in the wheels are seldom seen in practice.
More commonly, wheeled vehicles that employ adhering members integrated into the wheels employ a reduced or minimal number of wheels in wheel-based climbing systems. This can be seen in several examples in the literature including U.S. Pat. No. 6,627,004, U.S. Pat. No. 6,793,026 and U.S. Pat. No. 7,625,827. These typically employ either three wheels or four wheels. Three wheel systems enjoy the advantage of not requiring any type of suspension to insure contact of each wheel with the climbing surface when climbing on non-planar terrain. Four wheel systems are shown to incorporate a simple suspension design to maintain contact between the wheels and the climbing surface.
When a reduced number of wheels, for example three or four, are employed in a wheel-based climbing system, the forces required for equilibrium directed away from the surface will at times during operation be concentrated on a single wheel and associated adhering member. This concentration of forces on a single wheel results in a reduced payload capacity of the climbing vehicle. The payload capacity of climbing vehicles is one of the primary performance metrics in the design of such a vehicle. Thus, wheel-type climbing robot vehicles that place the adhering members in our about the wheels have limitations in the payload capacity.
Alternatively, the literature of wheel-type climbing robots demonstrates inventions that place the adhering members in the frame or chassis of the vehicle. An example of this is given in U.S. Pat. No. 3,810,515. This type of design is employed in a large number of commercially available climbing platforms. An example of such a commercial product is the Handiweld sold by Bug-O.
The design that places the adhering member directly in the chassis encounters significant performance limitations however when the system is used on a surface that is not flat, or has protrusions or indentions in the surface. This limitation arises from a technical difficulty that the chassis cannot conform to variations in the geometry of the climbing surface, such that the distance between the chassis and surface is changing during operation. The adhering force is typically strongly dependent on this distance, with an increase in distance between the adhering member and the climbing surface generally resulting in a decrease in adhering force. The decreased adhering force limits the available payload, thus limiting the performance of this type of invention.
The invention of this patent provides a novel means to overcome the limitations discussed for wheel-type climbing platforms. This invention provides a means to increase the number or magnitude of adhering force elements without increasing the number of wheels in a wheel-type climbing platform. The invention also provides a means to ensure or maintain a constant distance between the adhering force member and the climbing surface, to maintain the magnitude of adhering force during operation. Finally, the invention provides a means to distribute the loads required for equilibrium during climbing in an optimal manner over a large number of adhering members, while making sure that all wheel members stay in contact with the climbing surface.
When considering the prior art for climbing machines, with a focus on machines designed to climb ferrous surfaces using magnets, it is generally accepted that the climbing payload capacity is a function of the following components: 1) gross magnetic adhering force available, 2) the distribution of the gross magnetic adhering force, through a discrete number and location of individual magnetic elements, and 3) how the forces required for equilibrium in climbing are distributed among all the magnetic elements. Each of these components is considered in turn.                1) Gross magnetic adhering force available: The total magnetic attraction is generally not addressed as a limiting factor in the range of patents presented in climbing vehicle literature. The patent literature does not readily identify a need to optimize this force, and generally assumes that the magnetic force can be scaled.        2) Distribution of the gross magnetic adhering force through a discrete number and location of individual elements: The gross magnetic adhering force is generally discretized and distributed over the vehicle in one of three ways;                    a. discretized into a finite number of wheels (e.g., U.S. Pat. No. 7,625,827),            b. located in the chassis (e.g., U.S. Pat. No. 3,810,515),            c. distributed over the exterior surface of an endless track (e.g., U.S. Pat. No. 5,435,405),                        3) How the loads are distributed over the discretized magnet locations: For the wheel systems, with 4 wheels demonstrated, a maximum of three wheels can be employed on a general surface and therefore a redundancy of n−3 (with n=number of wheels) exists. The load thus can only be distributed to 3 wheels in the limiting case. This even occurs when mobility is added to the system to allow for movement of multiple wheels as seen in US pat. App. 2010/0176106. The rare example is U.S. Pat. No. 6,000,484 which calls out springs (kinetic constraints), but this patent does not identify a distribution means. For vehicles with the magnets located in the chassis, the adhering force is now a function of the distance between the chassis and the climbing surface. Thus, small displacements between the chassis and the climbing surface, caused by variations in the surface geometry, are greatly magnified and reduce the actual attraction force. For tracked systems with the adhering members or magnets located in the tracks, the difficulty becomes in simultaneously allowing the tracks to conform to the climbing surface while transferring forces between all elements along the track and the vehicle body. The majority of patents employing endless tracks with adhering members in the tracks do not provide a means to distribute climbing forces among the track elements.        There are a few special cases of note that do provide a means to distribute the climbing forces among more than 3 of the discrete magnets. U.S. Pat. No. 7,624,827 employs and endless track that surrounds a series of magnetic wheels, and provides a means to transfer both pulling and pushing forces from the wheels to the chassis. US application publication number US 2012/0111649 A1 shows a climbing vehicle with magnets attached to the endless track and provides a suspension that is slidably connected to the endless track to allow a means to transfer both pulling and pushing forces from all the adhering members to the chassis. A primary limitation of the U.S. Pat. No. 7,624,827 invention is that it does not permit a mechanism to return a distributed magnet back to the wall if the pulling force exceeds the magnet force. The primary limitation of US application publication number US 2012/0111649 A1 is that the tracks with exterior magnets create a non-constant pitch distance and therefor non-uniform velocity transmission between input and output.        
A closer inspection of the prior art considering wheel-type climbing vehicles shows a broad number and range of inventions. In general, these systems can be placed into two categories, those that place the adhering members as part of the wheel or those that place the adhering members as part of the vehicle body or chassis. Examples of the first category, wheel-type climbing vehicles with adhering members located in the wheels include U.S. Pat. No. 3,690,393, U.S. Pat. No. 4,010,636, U.S. Pat. No. 5,049,218, U.S. Pat. No. 5,355,807, U.S. Pat. No. 5,853,655, U.S. Pat. No. 6,000,484, U.S. Pat. No. 6,564,815, US 6,59622, U.S. Pat. No. 6,595,152, U.S. Pat. No. 6,627,004 B1 2003, U.S. Pat. No. 6,688,938, U.S. Pat. No. 6,793,026, U.S. Pat. No. 6,886,651, US pat. App. 2009/0078484, U.S. Pat. No. 7,309,464 B2, US pat. App. 2010/0212983 and US pat. App. 2010/017610. One of the earliest examples of such an early example of this system is U.S. Pat. No. 3,690,393 to create a toy car on track. This invention shows a four-wheel system, although other numbers of wheels have been shown with combinations of traditional and non-traditional wheels (U.S. Pat. No. 6,793,026). While the number of wheels is not specified or unique in the claims, and therefore not limiting to a large number of magnetic wheels, these patents do not address the kinematic constraints that are imposed when additional wheels are added in order to maintain wheel roll without slip. Additionally, these patents do not address potential slip conditions.
Some of the wheel-type inventions include adhering members in the wheels with the rotational axis of all wheels rigidly attached to a rigid platform. Alternatively, some inventions that include adhering members in the wheels (for example, US pat. App. 0212983) have some or all of the wheels pivotally connected to a member that is pivotally connected to the chassis allowing the wheel pivot movement relative to the chassis.
This patent presents a new invention for a climbing vehicle system. This invention places the adhering members (members that create an adhering force to the climbing surface) on a suspension member, called a resilient runner, which is attached to the vehicle chassis in a way that allows the resilient runner to move independently of the vehicle chassis to accommodate variations in the geometry of the climbing surface. Furthermore, the resilient runner is able to transfer forces between the chassis and the adhering members in a manner that distributes the loads required for equilibrium among multiple adhering members. The resilient runner can deform to accommodate large variations in the geometry of the climbing surface. This allows the adhering members to maintain a constant distance from the climbing surface to maintain the adhering force. Finally, the invention provides a mechanism by which the resilient runner will be automatically or self-attract to the climbing surface.